Electromagnetic radiation delivery apparatus

ABSTRACT

The invention relates to an electromagnetic radiation delivery apparatus ( 10 ) for tissue treatment, comprising a source of electromagnetic radiation ( 14 ), an emission window ( 16 ) which is optically coupled to the source of electromagnetic radiation ( 14 ) and is able to emit electromagnetic radiation, at least one recess ( 18 ) provided in a skin contact area, and a pressure gauge ( 20 ) for measuring a pressure inside the recess ( 18 ) or a pressure correlated therewith. In accordance with the invention electromagnetic radiation delivery apparatus ( 10 ) for tissue treatment comprises means ( 22 ) for creating an overpressure inside the recess ( 18 ).

The present invention relates to an electromagnetic radiation deliveryapparatus for tissue treatment, comprising a source of electromagneticradiation, an emission window which is optically coupled to the sourceof electromagnetic radiation and is able to emit electromagneticradiation, at least one recess provided in a skin contact area, and apressure gauge for measuring a pressure inside the recess or a pressurecorrelated therewith.

An apparatus of the type mentioned above is known from WO 2005/009266A1. The device disclosed in this document comprises vacuum means forcreating an underpressure in the recess. The underpressure can only bebuilt up or maintained, if the radiation delivery head of the apparatusis in proper contact with the skin to be treated. If the radiationdelivery head is not in proper contact with the skin to be treated, theunderpressure in the recess can not be built up or it collapses. This isdetected via the pressure gauge to make sure that no electromagneticradiation is emitted that could, due to the improper contact of theradiation delivery head and the skin to be treated, reach body parts notto be treated, such as eyes or skin parts of humans or animals nearby oreven other objects susceptible to being damaged by the electromagneticradiation.

A disadvantage of the apparatus known from WO 2005/009266 A1 is thatmovement of the apparatus over the skin may be hampered due to theunderpressure leading to skin being sucked into the recess.

It is the object of the present invention to further develop theapparatuses of the kind mentioned at the beginning such that movement ofthe apparatus over the skin is facilitated.

This object is solved by the features of the independent claims. Furtherdevelopments and preferred embodiments of the invention are outlined inthe dependent claims.

In accordance with the present invention there is provided anelectromagnetic radiation delivery apparatus for skin treatment of thetype mentioned at the beginning which comprises means for creating anoverpressure inside the recess. Preferably, the means for creating theoverpressure are formed by an electric air pump which feeds compressedair into the recess. However, other gases than air may be also used, ifthis is regarded as advantageous for certain kinds of skin treatments.The overpressure in the recess leads to a little leakage, i.e. a part ofthe compressed air is pressed out of the recess. Therefore, a cushion ofair (or of another gas) is created on which the skin contact area isplaced. This ensures that the apparatus may be easily moved over theskin to be treated. The pressure gauge may be a pressure meter combinedwith a display, a switch or other control means.

A preferred embodiment of the apparatus according to the invention isfurther characterized by control means connected to the pressure gaugeand to the source of electromagnetic radiation, wherein the controlmeans are able to prevent the electromagnetic radiation source and/orthe emission window from emitting electromagnetic radiation when thepressure measured by the pressure gauge is lower than a predeterminedthreshold value. Thereby, the risk of incorrect use is lowered evenfurther. The control means may be provided as for instance an electronicswitch or shutter. If an appropriate threshold value is set, it is notpossible to operate the apparatus when the pressure is below thatpredetermined value because there is no proper contact between the skincontact area and the skin to be treated. Consequently, even in the caseof operation by unfit people, e.g. small children, the risk of causingharm or danger is reduced. It is to be noted that in the context of thepresent application, “measuring” a pressure means either determining anabsolute value, or determining a relative value, e.g. with respect tothe predetermined threshold value. In that case it is not necessary todetermine the true pressure value, but only whether the pressure isabove or below the threshold value. The threshold value, i.e. thepressure value below which the apparatus should be turned off or isautomatically turned off by the control means may be appropriatelyselected in accordance with the properties of the body part or surfaceto be treated.

Advantageously, the threshold value is from 1 to 500 mbar above ambientpressure. If the body part or surface to be treated is smooth, flexibleand compressible, a low pressure difference may be selected, e.g. 10 or20 mbar above ambient pressure. If the surface to be treated is roughand incompressible, the threshold value should be much higher thanambient pressure, e.g. 200 mbar, in order to ensure a correct check ofthe position of the skin contact area. As mentioned above, it isadvantageous that part of the compressed air leaks out of the recesseven when the delivery head is in the correct position. The power of theoverpressure means should therefore be high enough for a sufficientpressure difference to be maintained in spite of the leaking of air. Ofcourse the threshold value can depend on the ambient pressure, whichmeans that e.g. in an area of low pressure or at a high altitude; thethreshold value is correspondingly lower than the threshold value in anarea of high pressure or at sea level. Preferably, the threshold valuedepends on the ambient pressure and it may be expressed as a pressuredifference with ambient pressure. In the presently preferred embodimentit is possible to define the threshold value as a pressure differencewith ambient pressure of between 1 and 500 mbar.

Preferably, during a period of time in which the measured pressureinside the recess is below the threshold value, the control means areable to prevent the electromagnetic radiation source from emittingelectromagnetic radiation above a predetermined maximum amount ofenergy. By allowing only a certain maximum amount of energy to beemitted during a session, overexposure of the skin, with possible(increased) discomfort or injury may be avoided. Moreover, there will beno more uncertainty whether or not a certain part of the skin receivedradiation. Since the electromagnetic radiation which is delivered to thebody part or surface to be treated affects said body part or surface, itmay be important to limit the total amount of supplied radiation. In apreferred embodiment, the control means are able to prevent re-operationof the apparatus, thereby ensuring that it is not possible to supplymore radiation energy than the predetermined maximum amount of energywithout lifting the delivery head and hence breaking the overpressure.

At least for some application areas it is advantageous that the controlmeans control a shutter that is able to prevent emission of theelectromagnetic radiation. Such a shutter may take any desired form,e.g. an electro-optical shutter, a mechanical shutter, a switchablemirror etc. An advantage of the presence of such a shutter is that theelectromagnetic radiation source need not be switched off when theapparatus is not to emit radiation. For many sources of electromagneticradiation this is beneficial to the lifetime of the source. However, iffrequent switching on and off of the electromagnetic radiation sourcedoes not substantially shorten the lifetime of the source, it is alsopossible for the control means to simply switch the power source of theelectromagnetic radiation source on and off, for example in the case ofLEDs and lasers.

In one embodiment, an emission window is present in the recess. The term“emission window” relates to an area, for example of a radiationdelivery head, through which electromagnetic radiation is emitted. Itmay come in the form of e.g. a piece of material that is transparent tothe electromagnetic radiation to be emitted, e.g. glass in the case ofoptical light. However, it may also mean an open side of a cavity whichis not covered by any material, e.g. an exit end of a tube. An advantageof an emission window being present in the recess is that when therecess is deemed to be positioned correctly, the emission window isautomatically positioned correctly as well. In most cases, one emissionwindow is present. However, it is to be noted that it is also possiblefor a plurality of emission windows to be present.

With another embodiment the recess surrounds the emission window. Thisis a slightly more general instance of the case in which the emissionwindow is present in the recess. If the recess surrounds the emissionwindow, then an appropriate overpressure in the recess guarantees acorrect positioning of the emission window. In this case the recess maycome in the form of a groove around the emission window. In this way itis possible to have different shapes for the recess and the emissionwindow. This offers advantages if the radiation is preferably suppliedin a circular pattern, e.g. for homogeneity reasons, whereas a differentpart of the surface surrounding the part which is treated should notreceive radiation. This part may of course have a different shape.Furthermore, it is also possible that a plurality of recesses isprovided. It may be contemplated that a number of small recesses ispresent in the form of a number of holes around the emission window. Ifall holes are positioned correctly, this too is a safe indication thatthe delivery apparatus is positioned correctly.

For all embodiments it may be advantageous that the recess comprises acircumferential edge. In this way it is relatively simple to visuallycheck the correct positioning by inspecting the circumferential edge.

Advantageously, the circumferential edge is flexibly deformable. Thisembodiment allows adaptation to a body part or surface not exactlymatching the plane of the emission window or recess. Although it ispossible to use a non-deformable skin contact area and delivery head,respectively, and to make use of the deformability of the body part or asurface to be treated, a flexibly deformable circumferential edge offersthe advantage that the pressure exerted on the body part or surfacediffers less. If the emission window is in the form of a transparentpiece of material, this piece of material may be used to exert pressureon the body part or surface to be treated. In this case, in particularin the case of skin, the bloodstream through said body part may beaffected. For instance in the case of photo hair removal, it isadvantageous if the blood circulation is reduced in the tissue beingtreated, because then there will be less absorption of radiation bytissue parts other than the intended parts (chromophores, hairfollicles). Besides, risks of possible side-effects of the treatment arereduced. The flexibly deformable circumferential edge may be designed asa rim of resilient material such as rubber. Any other flexiblydeformable material or construction is also possible.

In an advantageous embodiment, the circumferential edge lies on a planesurface, on a concave surface or on a convex surface. With these simplegeometries, most body parts or other surfaces to be treated can betreated efficiently. Plane surfaces may be used for treating e.g.artificial objects or small areas of large and hence relatively flatbody parts such as legs. A concave surface for the circumferential edgemay be useful when treating a convex body part, e.g. a relatively smallbody part such as a finger or other, strongly curved body parts such asa nose. A convex surface for the circumferential edge is advantageousfor the treatment of more or less concave surfaces, such as for thedepilation of arm pits. In specific cases other surfaces for thecircumferential edge may be even more advantageous.

In a preferred embodiment of the apparatus according to the invention,the electromagnetic radiation comprises infrared radiation, visibleoptical radiation or ultraviolet radiation. For the purpose of thepresent application, infrared radiation, visible optical radiation andultraviolet radiation will be referred to as “optical radiation”.Optical radiation is a part of the electromagnetic spectrum which ismost often used for the treatment of body parts, especially bynon-skilled or other private persons. In principle, however, it would bepossible to use other types of electromagnetic radiation, e.g. microwaveradiation or x-rays. The preferred electromagnetic radiation accordingto the invention (optical radiation) covers treatments by means of heat(infrared radiation) for treatment of muscle pain, depilation, treatmentof hyperbilirubinaemia, etc. by means of visible optical radiation, andartificial tanning and treatment of various skin disorders, such asvitiligo and psoriasis. Although some treatments may be performed bynon-skilled or non-professional personnel, such as tanning anddepilation, in many cases it may be preferable to have professionalskilled personnel perform the treatment. Nevertheless, also in the caseof professional personnel, the improved safety and other advantageousfeatures of the apparatus according to the invention are valid.Throughout the application the words “body part” and “surface to betreated” relate to any human tissue susceptible to a treatment by meansof electromagnetic radiation. In particular this relates to skin (humanskin). In general, however, any other treatable surface may becontemplated, e.g. in the field of materials research, curing ofmaterial. However, the invention has special advantages when used inrelation to treatment of humans or animals, since the risks ofinadvertent injury through accidents etc. are much reduced.

In the apparatus according to the present invention, the source ofelectromagnetic radiation may be arranged in a radiation delivery head.This means that e.g. a light source such as a LED or a high-pressure gasdischarge lamp is built into the radiation delivery head. However, in anadvantageous embodiment, the source of electromagnetic radiationcomprises electromagnetic radiation generating means and electromagneticradiation guiding means optically connected thereto. The presence of anelectromagnetic radiation generating means and electromagnetic radiationguiding means offers the possibility of separation of these twofunctions. This means that a complex, large and heavy electromagneticradiation generating means, such as a high power laser, may be presentat a certain distance from the delivery head. The delivery head, whicheventually emits the radiation generated by the electromagneticradiation generating means is optically connected to the electromagneticradiation guiding means so that the latter can guide the electromagneticradiation to the radiation delivery head, and eventually to the emissionwindow. This allows a relatively small and light-weight delivery head,which greatly improves the ease of use of the apparatus.

In an advantageous embodiment, the electromagnetic radiation guidingmeans comprise a mirror, a hollow electromagnetic radiation guide or anoptical fiber. The person skilled in the art will know how to select theappropriate guiding means. E.g. in the case of a laser, an optical fibermay be the guiding means of choice. A mirror may be used in the casewhere a laser is the electromagnetic radiation generating means and thelaser beam is used to scan a certain area to be treated. This allowssaid area to be illuminated homogeneously by the laser beam without theoperator having to move the radiation delivery head. This greatlyimproves the efficacy and homogeneity of the treatment.

Advantageously, the source of electromagnetic radiation comprises alaser, a flash lamp, a LED, a gas discharge lamp or an incandescentlamp. These electromagnetic radiation sources have proved to beefficient and useful in a wide variety of possible uses of the apparatusaccording to the invention. They come in a large variety of wavelengths,powers etc. Nevertheless, in particular cases, other sources may be usedalso, such as x-ray sources.

Advantageously, the at least one recess is formed by a groove having adepth which is greater than the width of the groove. The cross sectionof the groove, i.e. the relation between width and depth, is veryimportant. If the width of the groove is, for example, not larger than 3mm, the skin cannot touch the inner side of the groove even if it ispressed very strong against the device and vice versa. Skin doming cannot close the overpressure air supply of the groove. In general,different cross sections of the groove are possible, for examplerectangular, squared, half-rounded, triangular, or rounded triangular.

Additionally or alternatively it is possible that the recess is at leastpartly formed in the emission window, particularly in the surface of theemission window which is intended to contact the skin. There may, forexample, be provided grooves that are placed (also) on or in the exitwindow surface in such a way, that the overpressure air flows over thesurface in order to cool the skin. The shape of the groove on thesurface is, for example, meander-like arranged, or the air flows fromone to the other side in parallel groves. If there is a recessed window,the air, for example, flows also from one corner of the arrangement tothe other one.

In accordance with a further development of the present invention, therecess is formed in a treatment head of the apparatus, wherein at leasta part of the recess is arranged pivotable with respect to othercomponents of the treatment head. For example, the overpressuregroove-system can be mounted pivotable around the emission window whichmay be, for example, an astigmatic/cylindrical lens or a convex lens. Ifthe hand piece of the treatment head, where the optical- andoverpressure-system can be integrated, is pivoted on the skin, theoverpressure system and the lens is always in contact with the skin.They are laying in a plane surface. At least in some cases it may beadvantageous, if the pivotable overpressure system is spring loaded withrespect to the hand piece.

For the apparatus according to the invention it is preferred that thereare provided at least two overpressure ducts for creating theoverpressure in the at least one recess. In general providing at leasttwo overpressure ducts for each recess minimizes the risk that theoverpressure can not be build up due to a clogged duct.

The above and further aspects and advantages of the invention will beapparent from and elucidated with reference to the embodiments describedhereinafter and shown in the drawings, wherein:

FIG. 1 shows a schematic block diagram of a first embodiment of theapparatus in accordance with the present invention, wherein theapparatus comprises a main device and a treatment head connectedthereto;

FIG. 2 shows a schematic block diagram of a second embodiment of theapparatus in accordance with the present invention, wherein theapparatus is completely formed by a hand piece;

FIG. 3A shows a schematic block diagram of a part of a treatment head ofa third embodiment of the apparatus in accordance with the presentinvention, wherein emission window is recessed with respect to thesurrounding material;

FIG. 3B shows the part of the treatment head of FIG. 3A during treatmentof skin;

FIG. 4A shows a bottom view of a treatment head of a fourth embodimentof the apparatus in accordance with the present invention;

FIG. 4B shows a sectional view of a part of the treatment head of FIG.4A;

FIG. 5 shows a bottom view of a treatment head of a fifth embodiment ofthe apparatus in accordance with the present invention;

FIG. 6 shows a bottom view of a treatment head of a sixth embodiment ofthe apparatus in accordance with the present invention;

FIG. 7 shows a sectional view of a treatment head of a seventhembodiment of the apparatus in accordance with the present invention;

FIG. 8A shows a bottom view of a treatment head of an eighth embodimentof the apparatus in accordance with the present invention;

FIG. 8B shows a sectional view of a part of the treatment head of FIG.8A;

FIG. 9 schematically illustrates a possibility for feeding air into arecess;

FIG. 10 schematically illustrates a preferred geometry of a grooveforming the recess or being part thereof;

FIG. 11 shows an undesired skin doming effect resulting from adisadvantageous geometry of a groove;

FIG. 12 shows a reduces skin doming effect resulting from a advantageousgeometry of a groove;

FIG. 13 illustrates examples for possible cross sections of a grooveforming the recess or being part thereof;

FIG. 14A shows a groove having a triangular cross section together withan overpressure feeding duct associated to the groove;

FIGS. 14B, 14C, and 14D are cross sectional views corresponding to thesection lines A-A, B-B, and C-C of FIG. 14A;

FIG. 15 schematically illustrates a possible arrangement of adjacentgrooves;

FIG. 16 shows an emission window in the form of a convex lens, whereinan overpressure system is arranged pivotable with respect to theemission window and the further components of a treatment head;

FIG. 17A shows an emission window in the form of anastigmatic/cylindrical lens, wherein an overpressure system is arrangedpivotable with respect to the emission window and the further componentsof a treatment head;

FIG. 17B shows the arrangement of FIG. 17A in a tilted position;

FIG. 18A shows an example for a recessed, concave or convex emissionwindow which is surrounded by an overpressure ring system, wherein theoverpressure ring system is pivotable with respect to the emissionwindow and the further components of a treatment head; and

FIG. 18B shows the arrangement of FIG. 18A in a tilted position;

Throughout the drawings equal or similar reference numerals are used todenote equal or similar components, and at least some of thesecomponents are explained only once to avoid repetitions.

FIG. 1 shows a schematic block diagram of a first embodiment of theapparatus 10 in accordance with the present invention, wherein theapparatus comprises a main device 36 and a treatment head 34 connectedthereto. The main device 36 comprises a source of electromagneticradiation 14 consisting of an electromagnetic radiation generation means30 and electromagnetic radiation guiding means 32. The electromagneticradiation generating means 30 may comprise a laser, a flash lamp, a LED,a gas discharge lamp or an incandescent lamp. However, if theelectromagnetic radiation generating means 30 are located in the maindevice 36, it is preferred that a laser generates the radiation. Thesource of electromagnetic radiation 14 furthermore comprises radiationguiding means 32, which are shown as an optical fiber in FIG. 1 but canalso comprise a mirror or a hollow electromagnetic radiation guideand/or a radiation guiding crystal, particularly a crystal comprising atotal internal reflection. The optical fiber 32 guides theelectromagnetic radiation to an emission window 16 which is located inthe treatment head 34. The main device 36 furthermore comprises means 22for creating an overpressure, wherein the means 22 can be formed forexample by a suitable pump, as illustrated. By a pressure line 44 thepump 22 is connected to a recess 18 provided in the skin contact area ofthe treatment head 34. In the treatment head 34 there is furtherprovided a pressure gauge 20 for detecting the pressure inside therecess 18. The source of electromagnetic radiation 14 as well as thepump 22 are controlled by control means 24 which receive the outputsignal of the pressure gauge 20 via a wire 46. As may be seen, thecontrol means 24 are located within the main device 36, and the controlmeans 24 can, for example, comprise a microprocessor, memory means andfurther circuitry well known to the person skilled in the art.

The apparatus 10 can, for example, be a depilation apparatus. To preventthat electromagnetic radiation generated by the source ofelectromagnetic radiation 14 and emitted by the emission window 16reaches regions, for example, an eye of the user, the apparatus 10 worksas follows. If the treatment head 34 is in a proper contact with theskin to be treated, an overpressure is built up in the recess 18 whichis formed by a groove which completely surrounds the emission window 16.This overpressure is detected by the pressure gauge 20 which feeds hisoutput signal to the control means 24. If the control means 24 detectthat the overpressure is sufficiently high, it is assumed that thetreatment head 34 is in proper contact with the skin to be treated andthe control means 24 instruct the electromagnetic radiation generationmeans 30 to generate radiation which is fed to the skin to be treatedvia the optical fiber 32 and the emission window 16. If the overpressurein the recess 18 decrease due to an improper contact of the treatmenthead 34 and the skin to be treated, the control means 24 detect the dropin pressure via the output signal of the pressure gauge 20. To avoidthat the user (or any other person) is hurt by radiation, the controlmeans 24 immediately instructs electromagnetic radiation generatingmeans 30 to stop generating radiation. In case of a proper contactbetween the treatment head 34 and the skin to be treated, a cushion ofair is created on which the skin contact area of the treatment head 34can glide during operation. Furthermore, an overpressure has theadvantage that clogging of the opening or openings will be hampered. Assoon as there is dirt or any kind of impurity, the little air flow outof the openings help to blow away these impurities, like skin flakesfrom tissue (epidermis), dust or something like this.

FIG. 2 shows a schematic block diagram of a second embodiment of theapparatus 10 in accordance with the present invention. The componentsshown FIG. 2 essentially correspond to the components discussed withreference to FIG. 1, and, to avoid repetitions, reference is made to thecorresponding description. However, with the embodiment shown in FIG. 2,the apparatus 10 is completely formed by a hand piece, and therefore,all components are arranged within the hand piece. In addition to thecomponents discussed with reference to FIG. 1, the embodiment of FIG. 2further comprises a shutter 26 which is suitable to cover the emissionwindow 16 such that no radiation is emitted, even if radiation isgenerated by the source of electromagnetic radiation 14. The shutter 26is activated by the control means 24, if an insufficient overpressure inthe recess 18 surrounding the emission window 16 is detected due to animproper contact of the skin contact area and the skin to be treated.

FIG. 3A shows a schematic block diagram of a part of a treatment head 34of a third embodiment of the apparatus 10 in accordance with the presentinvention, wherein emission window 16 is recessed with respect to thesurrounding material 48, and FIG. 3B shows the part of the treatmenthead 34 of FIG. 3A during treatment of skin 42. Between the transparentemission window 16, where the radiation is coming out, and the skin 42to be treated, there is a certain distance of a couple of millimetersforming a recess 18. The surrounding material 48 is reflective or atleast not transparent, or it consists of a material that scatters thelight like skin. Aim is not to lose radiation that is scattered backfrom the skin to the surrounding material 48. As may be seen in FIG. 3B,this arrangement is pressed onto the skin 42 during treatment. Betweenthe emission window 16 and the skin 42 a cavity of recess 18 is formed.A pump 22 produces an overpressure in the recess 18, similar asdescribed above for the recess 18 in form of a groove. If the edges ofthe surrounding material 48 around the emission window 16 are pressedquite well to the skin 42, the pressure in the recess 18 can increase toa defined level which has to be higher than the air pressure that isavailable around the device, as discussed above. As regards the safetyfunction of this arrangement, reference is made to the correspondingdescription in connection with FIG. 1.

FIG. 4A shows a bottom view of a treatment head of a fourth embodimentof the apparatus in accordance with the present invention, and FIG. 4Bshows a sectional view of a part of the treatment head of FIG. 4A. Asmay be seen, with this embodiment the skin contact area comprises arectangular geometry. The emission window 16 is surrounded by a recess18 in form of a groove. The groove 18 is connected to a pressure gauge20 and a pump 22, as discussed with reference to FIG. 1. As may be bestseen in FIG. 4B, the emission window and the surrounding material 48form a common skin contact plane. The surrounding material 48 forms acircumferential edge 28 which may be flexibly be formable to enhance theceiling function.

FIG. 5 shows a bottom view of a treatment head of a fifth embodiment ofthe apparatus in accordance with the present invention. With thisembodiment the skin contact area comprises a circular geometry. Exceptthat, the configuration corresponds to the embodiment of FIG. 4A andFIG. 4B.

FIG. 6 shows a bottom view of a treatment head of a sixth embodiment ofthe apparatus in accordance with the present invention. With thisembodiment, the skin contact area comprises a substantially rectangulargeometry; however, the corners and the groove are rounded. Except that,the configuration corresponds to the embodiment of FIGS. 4A and 4B.

FIG. 7 shows a sectional view of a treatment head of a seventhembodiment of the apparatus in accordance with the present invention.With this embodiment the recess or groove 18 is not separately formedbut is formed partly by the emission window 16 and the slanted edge ofthe surrounding material 48. With such an arrangement it is advantageousto provide a suitable sealing 50 between the emission window 16 and thesurrounding material 48.

FIG. 8A shows a bottom view of a treatment head of an eight embodimentof the apparatus in accordance with the present invention, and FIG. 8Bshows a sectional view of a part of the treatment head of FIG. 8A. Withthis embodiment the recess 18 is at least partly formed in the skincontact area of the emission window 16. As may be seen a meander-likegroove 18 is provided, which is connected to the pressure gauge 20 andthe pump 22. Thereby, the overpressure air is flowing on the surface andcools the skin which is treated.

FIG. 9 schematically illustrates a possibility for feeding air into arecess 18. As may be seen, the recess 18 is provided in form of a groovehaving a rectangular cross section. A duct 52, which may be regarded asa part of the overpressure generating means 22, is provided to feed airinto the recess 18. A similar duct may be provided on the other end ofthe groove to connect the recess 18 with the pressure gauge.

FIG. 10 schematically illustrates a preferred geometry of a grooveforming the recess or being part thereof. The cross section, i.e. therelation between width and depth of the groove, is very important. Bestresults may be obtained, if the width at the skin contact area issmaller than the depth of the groove. If the width of the groove 18 is,for example, not more than 3 mm, the skin can not touch the inner sideof the groove 18, even if it is pressed very strong to the device andvice versa.

FIG. 11 shows an undesired skin doming effect resulting from adisadvantageous geometry of a groove. As may be seen, if the groove 18is not deep enough, it is possible that skin touches the inner side ofthe groove, and in the worst case seals the duct leading to the pressuregauge, whereby the safety function could be disabled.

FIG. 12 shows a reduced skin doming effect resulting from anadvantageous geometry of a groove. As may be seen, skin doming stilloccurs, but the skin can not touch the inner side of the groove sincethe depth of the groove is greater than the width thereof.

FIG. 13 illustrates examples for possible cross sections of a grooveforming the recess or being part thereof. From the left to the right thefollowing cross sections of a groove 18 are shown: rectangular, squared,half-rounded, triangular, and rounded-triangular. All these geometriesmay be used, while it is still preferred that the width of the groove 18is smaller than the depth thereof.

FIG. 14A shows a groove having a triangular cross section together withan overpressure feeding duct 52 associated to the groove 18 and FIGS.14B to 14D are cross sectional views corresponding to the section linesA-A, B-B, and C-C of FIG. 11A. As may be seen from FIGS. 14A and 14B itis preferred that the duct 52 for feeding the pressurized air is locatedin the centre. This is preferred to avoid that the duct 52 is clogged bythe skin doming.

FIG. 15 schematically illustrates a possible arrangement of adjacentgrooves 18. There are shown three adjacent grooves 18, each having atriangular cross section and a central duct 52 for feeding pressurizedair. The grooves 18 overlap and the sealing function with reference tothe skin 42 is provided by the circumferential edges 28.

FIG. 16 shows an emission window 16 in the form of a convex lens,wherein an overpressure system 38 is arranged pivotable with respect tothe emission window 16 and the further components of a treatment head34. If the hand piece or treatment head 34, in which the optical systemand/or the overpressure pump may be integrated, is pivoted or treatedwith respect to the skin 42, the overpressure system 38 comprising thegroove 18 and the convex lens is always in contact with the skin 42. Itmay be advantageous, if the overpressure system 38 is spring loaded bysprings 40 to achieve an optimal contact between the overpressure system38 and the skin 42.

FIG. 17A shows an emission window 16 in the form of anastigmatic/cylindrical lens, wherein an overpressure system 38 isarranged pivotable with respect to the emission window 16 and thefurther components of a treatment head, and FIG. 17B shows thearrangement of FIG. 17A in a tilted position. Except the lensconfiguration and the missing springs, the embodiment of FIGS. 17A and17B is similar to the embodiment of FIG. 16.

FIG. 18A shows an example for a recessed, concave or convex emissionwindow 16 which is surrounded by an overpressure ring system 38, whereinthe overpressure ring system 38 is pivotable with respect to theemission window 16 and the further components of a treatment head 34,and FIG. 18B shows the arrangement of FIG. 18A in a tilted position. Theconfiguration of the embodiment shown in FIGS. 18A and 18B is verysimilar to the configuration shown in FIG. 16. However, in accordancewith the embodiment of FIGS. 18A and 18B the hand piece comprises a heatsink 54 to dissipate heat generated by the source of electromagneticradiation 14. Furthermore, with the illustrated embodiment, it ispreferred that there is provided an AR-coating on parts of the emissionwindow 16. With such an arrangement radiation passes the emission window16 without losses, independent of the angle between the overpressuresystem 38 and the emission window 16. The light-unit is mountedpivotable around the central axis of the emission window 16. Althoughnot shown, the overpressure system may be spring loaded, as discussed inconnection with FIG. 16.

Equivalents and modifications not described above may also be employedwithout departing from the scope of the invention, which is defined inthe accompanying claims.

1. An electromagnetic radiation delivery apparatus for tissue treatment,comprising: a source of electromagnetic radiation, an emission windowwhich is optically coupled to the source of electromagnetic radiationand is able to emit electromagnetic radiation, at least one recessprovided in a skin contact area, and a pressure gauge for measuring apressure inside the recess or a pressure correlated therewith,characterized in that it comprises means for creating an overpressureinside the recess.
 2. The apparatus according to claim 1, whereincontrol means are connected to the pressure gauge and to the source ofelectromagnetic radiation, and wherein the control means are able toprevent the electromagnetic radiation source and/or the emission windowfrom emitting electromagnetic radiation when the pressure measured bythe pressure gauge is lower than a predetermined threshold value.
 3. Theapparatus according to claim 2, wherein the threshold value is from 1 to500 mbar above ambient pressure.
 4. The apparatus according to claim 2wherein during a period of time in which the measured pressure insidethe recess is below the threshold value, the control means prevent theelectromagnetic radiation source and/or the emission window fromemitting electromagnetic radiation above a predetermined maximum amountof energy.
 5. The apparatus according to claim 2, wherein the controlmeans control a shutter that is able to prevent emission of theelectromagnetic radiation.
 6. The apparatus according to claim 1,wherein the emission window is present in the recess.
 7. The apparatusaccording to claim 1, wherein the recess surrounds the emission window.8. The apparatus according to claim 1, wherein the recess comprises acircumferential edge.
 9. The apparatus according to claim 8, wherein thecircumferential edge is flexibly deformable.
 10. The apparatus accordingto claim 8, wherein the circumferential edge lies on a plane surface, ona concave surface or on a convex surface.
 11. The apparatus according toclaim 1, wherein the at least one recess is formed by a groove having adepth which is greater than the width of the groove.
 12. The apparatusaccording to claim 1, wherein the recess is at least partly formed inthe emission window.
 13. The apparatus according to claim 1, wherein therecess is formed in a treatment head of the apparatus, and wherein atleast a part of the recess is arranged pivotable with respect to othercomponents of the treatment head.
 14. The apparatus according to claim1, wherein there are provided at least two overpressure ducts forcreating the overpressure in the at least one recess.